Derek Hough, who is partnered with Olympic gold medalist gymnast Shawn Johnson, has revealed he is injured and going to have to miss this week's Dancing with the Stars: All-Stars rehearsals.

"There's something wrong with my vertebrae in my neck. I've had it before in the past a couple times, but this has probably been the worst. So just to take precaution, I think next week, I'm going to have to step out a little bit and have Mr. M.B. -- [fellow professional dancer] Mark Ballas -- step in with his previous partner, which I'm sad about -- to step out," Hough explained during last night's live Dancing with the Stars: All-Stars results show.

"I'm going to take precaution for the week, but I just don't want to let [Shawn] down. I feel extremely terrible, especially since she has her own issues."

Hough may miss Monday night's performance show as well due to his injury, but Ballas -- who won Dancing with the Stars eighth season with Johnson in 2009 -- is apparently ready to take his place whenever necessary. 

In an interview with E! News after the results show, Johnson elaborated a little more on Hough's condition.

"Derek's at a doctor's appointment right now. He's taking the week to rest up, get every doctor to look at him and kind of look things over. Mark is stepping in for rehearsals right now. Derek will still be there to choreograph and kinda oversee, but Mark will be doing the movement. And then, depending on the injury, depending on how he feels, it's up in the air as to whether he'll be on the show Monday or not," Johnson told E! News.

"If anybody were to step in, it'd be Mark. I love Mark and I love Derek. I cheated on Mark the first time, now I'm cheating on Derek. It's kind of a weird triangle going on."

During last night's results show, Johnson told Dancing with the Stars co-host Brooke Burke-Charvet she just wanted Hough to get better and that's what she cared about most.

"It's hard. I saw it kind of when it happened yesterday. I could just tell he had pain in his face, and I hate that. You feel helpless. You want to help, but take a week off and get better," said Johnson while looking at Hough.